Method of removing manganese containing deposits



United States Patent US. Cl. 134-3 7 Claims ABSTRACT OF THE DISCLOSURE Amethod of removing manganese containing deposits formed on the surfacesof jet engines from burning fuel containing a cyclopentadienyl manganesetricarbonyl as a smoke reducer, by treating the deposit coated surfaceswith an aqueous solution of an acidic nitrogen containing chelatingcompound.

Ethylene diamine tetraacetic acid (EDTA), nitrilotriacetic acid (NTA),and the disodium salt of EDTA are useful chelating compounds.

BACKGROUND OF THE INVENTION Smoke produced during the operation of adistillate fuel burning engine, such as a jet engine, is undesirable. Itcontributes to air pollution. It indicates reduced engine efficiency.

This exhaust smoke may be reduced by adding suitable additives to thefuel. Especially effective additives are certain cyclopentadienylmanganese tricarbonyls, such as (methylcyclopentadienyl)manganesetricarbonyl. US. 2,818,417 provides a thorough list of useful compoundsof this type, and includes methods of preparing them. Although use ofthese manganes additives substantially reduces the exhaust smoke, asecondary problem may arise in some instances. On combustion of the fuelcontaining the manganese compound, manganese containing deposits areformed on the engine surface which are contacted by the exhaustproducts. As with many engine deposits, an effective method of removingthese manganese containing deposits is desirable.

SUMMARY OF THE INVENTION A method of removing manganese containingdeposits formed on the surfaces of jet engines which burn fuelscontaining organo manganese compounds, which comprises treating thedeposit coated surfaces with an aqueous solution of an acidic nitrogencontaining chelating com pound.

Thus, manganese containing deposits formed in jet engines can be removedby treating the deposit coated surfaces with an aqueous solution of achelating compound such as ethylenediamine-tetraacetic acid. Thisprovides a simple and effective method for cleaning the engine; it isespecially advantageous because the engine can be cleaned withoutdisassembling it.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of this inventionis a method of removing manganese containing deposits formed on thesurfaces of a jet engine from burning a fuel containing a smoke reducingquantity of a cyclopentadienyl manganese tricarbonyl having up to 17carbon atoms, which comprises treating said surfaces with an aqueoussolution of an acidic chelating compound selected fromacids having theformulae wherein R, R R R and R are selected from alkyl groups havingfrom 1 to about 4 carbon atoms; M is selected from and L is selectedfrom hydrogen, C -C alkyl groups and C C aryl groups and n is selectedfrom 0 and 1, and partial salts of said acids.

Another embodiment of said method comprises treating the manganesecontaining deposit coated surface with an aqueous solution containing upto about 20 percent by weight 'of the chelating com-pounds describedabove.

In a preferred embodiment, the chelating compound is nitrilotriaceticacid or ethylenediamine tetraacetic acid (EDTA). A most preferredembodiment utilizes a saturated EDTA solution.

Manganese compounds which are useful as smoke reducers in jet fuels arecyclopentadienyl manganese tricarbonyls having the formula wherein R isa cyclopentadienyl hydrocarbon radical having from 5 to 17 carbon atoms.US. 2,818,417, issued Dec. 31, 1957, contains an extensive disclosure ofthe type of manganese compounds which are useful. This listing ofcompounds is incorporated by reference.

.(Methylcyclopentadienyl)manganese tricarbonyl is an especiallyelfective smoke reducer.

The concentration of the manganese tricarbonyl in the jet fuel may bevaried. Concentrations from 0.025 to about 6.45 grams of manganese pergallon as a cyclopentadienyl manganese tricarbonyl are useful.

By jet fuels, we include distillate hydrocarbons and blends which areuseful as fuel for jet engines. These fuels are principally hydrocarbondistillates heavier than gasoline. In other words they are distillatehydrocarbon fuels having a higher end point than gasoline. They aregenerally composed of distillate fuels and naphthas and blends of theabove, including blends with lighter hydrocarbon fractions. The endpoint of preferable jet fuels is at least 435 F and more preferablygreater than 470 F.

Typical jet fuels includes JP-3, a mixture of about 70 percent gasolineand 30 percent light distillate having a percent evaporation point of470 F.- JP-4, a mixture of about 65 percent gasoline and 35 percentlight distillate especially designed for high altitude performance;JP-S, an especially fractionated kerosene and the like.

The manganese containing deposit which is formed on the jet enginesurfaces comprises a mixture of compounds. Principal components of thismixture are the oxides such as Mn O and Mn O Acidic chelating compoundswhich are useful in the present method are nitrogen-containing polybasicacids, and partial salts thereof. The acids are represented by thefollowing formulae:

R, R R R and R are selected from alkyl groups having from 1 to about 4carbon atoms; M is selected from and L is selected from hydrogen, C -Calkyl groups and C C aryl groups, n is selected from and 1. Examples ofuseful chelating acids are trimethylene diamine tetraacetic acid,methylamine-diacetic acid, aminomethylphosphonic acid-N,N-diacetic acid,anilinediacetic acid, butylnitriloaminedimethylenediphosphonic acid,tetramethylene dinitrilotetramethylenetetraphosphonic acid, and thelike.

Ethylene diamine tetraacetic acid and nitrilotriacetic acid arepreferred chelating acids.

The partial salts of the chelating acids having Formulas I and II arealso useful. A partial salt is a salt obtained by using less than thestoichiometric amount of base required to neutralize all the acidgroups. For example, four moles of potassium hydroxide are required tofully neutralize one mole of ethylene diarnine tetraacetic acid (EDTA).By reacting only two moles of potassium hydroxide with one mole of EDTA,only two acid groups in the EDTA are neutralized. The product obtainedis a partial salt as represented by the formula 0 O KO 0 N(CHz)z-N-CIR-0 CH2 2 OH Thus the partial salts are characterized by having atleast one unneutralized acid group.

Bases which can be used to prepare suitable partial salts are inorganicbases such as sodium hydroxide, barium hydroxide, calcium hydroxide,ammonium hydroxide and the like; or organic bases such asdirnethylamine, diethylenetriamine, aniline, ethanolamine and the like.

Examples of useful partial salts are mono-calcium salt ofethylenediamine tetraacetic acid, disodium salt of ethylenediaminetetraacetic acid, monosodium salt of nitrilotriacetic acid and the like,mono-potassium salt of trimethylenedinitrilotetraethylenetetraphosphonicacid, monotrimethylamine salt of ethylenediamine tetrabutyric acid andthe like.

The concentrations of acidic chelating compound which are used in thepresent process may be varied. In general, concentrations of from about0.001 percent to about percent by weight are useful. Saturated solutionsare especially useful.

An outstanding feature of the present invention is that it offers amethod of removing manganese containing deposits in a jet engine wtihoutrequiring its disassembly or its removal from its mounting. Thus, theengine can be cleaned while it is still in place in an airplane fuselagefor example, by simply spraying the solution of acidic chelatingcompound described above, through the engine, while the engine is beingcranked. Cranking a jet engine means that the engine is turning but thefuel is not ignited. By cranking the engine, all the engine surfaceswhich may have a manganese containing deposit become exposed to thespray.

Another method of spraying the solution into the jet engine is to feedit through the fuel feed system between the fuel tank and the combustionarea. Using this procedure, the solution will contact only those enginesurfaces on which the fuel and exhaust products would iminge. The engineis cranked to insure better contact. In either case, the spray may becontinuously recycled if desired, to reduce the volume of solutionrequired. Besides the spraying technique, the engine can be cleaned byimmersing it in a suitably designed vessel containing the acidicchelating compound solution for a period of time sufficient to dissolvethe manganese containing deposits. After such an immersion or after aspray treatment, the engine is generally rinsed with a pure water. Acombination of the spray soak procedure can also be used.

The engine treatment can be carried out either before or after theengine has cooled after being in operation. The solution with which thetreatment is carried out may also be warmed, if desired. By treating theengine while hot or by using a hot solution, treatment time to clean theengine can be reduced. Heating either the engine surfaces or thesolution, however, is not required. Whatever means is used to carry outthe engine treatment, the only requirement is that a solution, as hereindescribed contact the manganese containing deposits on the enginesurfaces.

The effectiveness of the aqueous solution of acidic chelating compoundtreatment was determined in a laboratory procedure using a metal testspecimen on which was deposited a managanese containing deposit. Thetest specimen was prepared by allowing the exhaust stream from burning ajet fuel containing about 0.1 volume percent (1.29 g./gal. of manganese)of (methylcyclopentadienyl)manganese tricarbonyl, to impinge on themetal piece. The manganese containing deposit appeared as a brownish tandeposit on the metal surface. This test specimen was then immersed in avessel containing about 200 part of the aqueous solution of the acidicchelating compound to be tested. The solution was then warmed in a steambath to above about 70 C. The effect of the solution on the deposit wasobserved. The effective aqueous acid solutions dissolved a substantialportion of the tan manganese containing deposit, leaving the metal piecepartically free of the deposit. This dissolution began almostimmediately on placing the specimen in the test solution and wasconsidered to be practically complete after about 15 minutes of warmingon the hot plate.

Using this test procedure, a saturated aqueous solution ofethylenediaminetetraacetic acid was found to dissolve the manganesecontaining deposit very readily. A saturated solution ofnitrilo-triacetic acid was also found to be effective.

Similar results are obtained using a 0.001 percent solution of(p-tolylimino)diacetic acid; a 5 percent solution oftrimethylenedinitrilotetramethylene phosphoric acid; a two percentsolution of a monocaleium salt of ethylene-diaminetetraacetic acid; aone percent solution 3,3- {2-[bis(carboxymethyl)amino]ethyl)imino}dipropionic acid; a three percent solution ofmethylnitrilo-diphosphonic acid; or a 20 percent solution ofmonopotassium salt of nitrilotriacetic acid, in the test proceduredescribed above.

The results presented above clearly demonstrate that the manganesecontaining deposits formed on jet engine parts can be effectivelyremoved by treatment with an aqueous solution of an acidic chelatingcompound as herein described. The manganese containing deposit has beendescribed as that being formed from burning jet fuel containing acyclopentadienyl manganese tricarbonyl. However, it is considered withinthe scope of the present invention that the present method will beeffective for removing manganese containing deposits obtained on burningjet fuel containing other manganese bearing additives.

The process of the present invention is described above. It is intendedthat the present invention be limited only within the lawful scope andextent of the following claims.

I claim:

1. A method of removing manganese containing deposits formed on surfacesof a jet engine from burning a fuel containing a cyclopentadienylmanganese tricarbonyl compound wherein the cyclopentadienyl radical hasup to 17 carbon atoms, which comprises treating said surfaces with anaqueous solution of an acidic chelating compound selected from polybasicacids having the formula wherein R, R R R and R are hydrocarbon alkylgroups having from 1 to about 4 carbon atoms, M is selected fromsolution contains from 0.001 percent to about 20 percent by weight ofsaid chelating compound.

3. The method of claim 1 wherein said aqueous solutions is a saturatedsolution.

4. The method of claim 2 wherein said chelating compound isethylenediamine tetraacetic acid.

5. The method of claim 2 wherein said chelating compound isnitrilotriacetic acid.

6. The method of claim 3 wherein said chelating compound isethylenediamine tetraacetic acid.

7. The method of claim 3 wherein said chelating compound isnitrilotriacetic acid.

References Cited UNITED STATES PATENTS 2,396,938 3/1946 Bersworth 134-22,992,995 7/1961 Arden 134-20 XR 3,025,189 3/1962 Arden 134-3 3,033,2145/1962 Bersworth et a1. 134-22 XR 3,216,857 11/1965 DuVall 134-33,297,580 1/1967 Pitzer 252-142 MORRIS O. WOLK, Primary Examiner L isselected from hydrogen, C -C alkyl groups and 25 ZATAR, AssistantExaminer G -C aryl groups and n is selected from 0 to 1 and partialsalts of the (i) and (ii) type acids.

2. The method of claim 1 wherein the said aqueous US. Cl. X.R. 134-22,41

